[RFC][PATCH 3/4] kernel, power: disable printk_kthread in unsafe places

[Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>]

It's not always possible/safe to wake_up() printk kernel
thread. For example, late suspend/early resume may printk()
while timekeeping is not initialized yet, so calling into the
scheduler may result in recursive warnings. Thus we need
printk() to operate in old mode there and attempt to immediately
flush pending kernel message to the console. This patch adds
console_printing_thread_off/on sections.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 kernel/kexec_core.c      | 4 ++++
 kernel/power/hibernate.c | 8 ++++++++
 kernel/power/suspend.c   | 4 ++++
 3 files changed, 16 insertions(+)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index bfe62d5b3872..b40fba31150c 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1496,6 +1496,8 @@ int kernel_kexec(void)
 		goto Unlock;
 	}
 
+	console_printing_thread_off();
+
 #ifdef CONFIG_KEXEC_JUMP
 	if (kexec_image->preserve_context) {
 		lock_system_sleep();
@@ -1565,6 +1567,8 @@ int kernel_kexec(void)
 	}
 #endif
 
+	console_printing_thread_on();
+
  Unlock:
 	mutex_unlock(&kexec_mutex);
 	return error;
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index a8b978c35a6a..15634841ccc6 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -502,6 +502,7 @@ int hibernation_restore(int platform_mode)
 {
 	int error;
 
+	console_printing_thread_off();
 	pm_prepare_console();
 	suspend_console();
 	pm_restrict_gfp_mask();
@@ -519,6 +520,7 @@ int hibernation_restore(int platform_mode)
 	pm_restore_gfp_mask();
 	resume_console();
 	pm_restore_console();
+	console_printing_thread_on();
 	return error;
 }
 
@@ -542,6 +544,7 @@ int hibernation_platform_enter(void)
 		goto Close;
 
 	entering_platform_hibernation = true;
+	console_printing_thread_off();
 	suspend_console();
 	error = dpm_suspend_start(PMSG_HIBERNATE);
 	if (error) {
@@ -589,6 +592,7 @@ int hibernation_platform_enter(void)
 	entering_platform_hibernation = false;
 	dpm_resume_end(PMSG_RESTORE);
 	resume_console();
+	console_printing_thread_on();
 
  Close:
 	hibernation_ops->end();
@@ -692,6 +696,7 @@ int hibernate(void)
 		goto Unlock;
 	}
 
+	console_printing_thread_off();
 	pm_prepare_console();
 	error = __pm_notifier_call_chain(PM_HIBERNATION_PREPARE, -1, &nr_calls);
 	if (error) {
@@ -759,6 +764,7 @@ int hibernate(void)
  Exit:
 	__pm_notifier_call_chain(PM_POST_HIBERNATION, nr_calls, NULL);
 	pm_restore_console();
+	console_printing_thread_on();
 	atomic_inc(&snapshot_device_available);
  Unlock:
 	unlock_system_sleep();
@@ -868,6 +874,7 @@ static int software_resume(void)
 		goto Unlock;
 	}
 
+	console_printing_thread_off();
 	pm_prepare_console();
 	error = __pm_notifier_call_chain(PM_RESTORE_PREPARE, -1, &nr_calls);
 	if (error) {
@@ -884,6 +891,7 @@ static int software_resume(void)
  Finish:
 	__pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
 	pm_restore_console();
+	console_printing_thread_on();
 	atomic_inc(&snapshot_device_available);
 	/* For success case, the suspend path will release the lock */
  Unlock:
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 15e6baef5c73..7c6e228b7de4 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -433,6 +433,7 @@ int suspend_devices_and_enter(suspend_state_t state)
 	if (!sleep_state_supported(state))
 		return -ENOSYS;
 
+	console_printing_thread_off();
 	error = platform_suspend_begin(state);
 	if (error)
 		goto Close;
@@ -462,6 +463,7 @@ int suspend_devices_and_enter(suspend_state_t state)
 
  Close:
 	platform_resume_end(state);
+	console_printing_thread_on();
 	return error;
 
  Recover_platform:
@@ -520,6 +522,7 @@ static int enter_state(suspend_state_t state)
 #endif
 
 	pr_debug("PM: Preparing system for sleep (%s)\n", pm_states[state]);
+	console_printing_thread_off();
 	pm_suspend_clear_flags();
 	error = suspend_prepare(state);
 	if (error)
@@ -537,6 +540,7 @@ static int enter_state(suspend_state_t state)
  Finish:
 	pr_debug("PM: Finishing wakeup.\n");
 	suspend_finish();
+	console_printing_thread_on();
  Unlock:
 	mutex_unlock(&pm_mutex);
 	return error;
-- 
2.12.0